1. Field of the Invention
The present invention relates generally to pontoon boats characterized generally by a pair of pontoon logs held in spaced parallel relation by deck beams. More particularly, the invention relates to the method of attaching the deck beams to the pontoon logs and the pontoon log construction resulting from said method.
2. Description of Related Art
Pontoon boats, also known simply as pontoons, are increasing in popularity in view of their stability, large capacity, low maintenance and safety. A particular advantage of a pontoon boat is the fact that the pontoon logs are sealed, and the boat will not take on water from spray, waves or rain. The logs can be filled with a closed cell foam to ensure the requisite degree of flotation even in the event of log rupture, as might occur upon grounding or collision.
The construction of the pontoon logs have been generally of two different types; the more common log construction comprising a U-shaped hull in section to which is attached a flat top plate, and the less common cylindrically shaped log. The latter type of log presents particular difficulties in the attachment of the deck beams, requiring brackets or saddles involving log penetrating fittings which present the possibility of leakage.
With the U-shaped log hull shape, to which the present invention is directed, the transverse deck beams which join the logs and which support the pontoon deck are more readily attached to the logs in view of the planar log top surfaces. In a known construction, the sheet metal skin defining the U-shaped hull of the log includes outturned flanges along its upper edge where it intersects the log top plate. The edges of the log top plate extend over the hull flanges and the log top and hull are joined by welding the overlapped log top and flanges along their outer edges. The deck beams are attached by bolting through the lapped hull flanges and top plate. However, since the bolts are located interiorly of the weld line, the bolts must be sealed by caulking to prevent water penetration into the log interior. With time, the working of the bolts and the deterioration of the caulking material results in the passage of water into the log interior.
An alternate method of securing the hull flange to the top plate and for securing the deck beams to the hull is shown in U.S. Pat. No. 4,777,898, issued Oct. 18, 1988. This patent proposes the use of a sealing tape the length of the log joint between the hull flange and the top plate. A U-shaped clip having gripping toothed internal surfaces is forced over the sandwiched hull flange, seal strip and top plate, following which fastening means such as rivets are positioned at intervals along the edge to form a sealed log which does not require caulking. The attachment of the deck beams is accomplished by through-bolting through the clip and the enclosed top plate, seal strip and hull flange.
This patented construction has not proved entirely watertight and adds additional elements to the joint such as the clip and the seal strip with a consequent additional material and labor expense. Furthermore, the construction introduces assembly complexities, particularly at the bow of the logs where transition is made to a welded construction.